Vehicle apparatus and method

ABSTRACT

The present invention relates to a vehicle ( 1 ) having a torque generating machine ( 4 ); and one or more driven wheel (W D ). A driveline ( 6 ) is provided for transmitting torque from the torque generating machine ( 4 ) to said one or more driven wheel. The driveline ( 6 ) includes a torque transmitting means ( 8 ). A first decoupling mechanism ( 11 ) is operable to decouple the torque transmitting means ( 8 ) from the torque generating machine ( 4 ). The first decoupling mechanism ( 11 ) is closed to couple the torque transmitting means ( 8 ) to the torque generating machine ( 4 ) and is opened to decouple the torque transmitting means ( 8 ) from the torque generating machine ( 4 ). A second decoupling mechanism ( 12 ) is operable to decouple the torque transmitting means ( 8 ) from the one or more driven wheel. The second decoupling mechanism ( 12 ) is closed to couple the torque transmitting means ( 8 ) to the one or more driven wheel and is opened to decouple the torque transmitting means ( 8 ) from the one or more driven wheel. A controller ( 2 ) is provided having at least one electronic processor for controlling operation of the first and second decoupling mechanisms ( 11, 12 ). The at least one electronic processor (P) is configured to close the first decoupling mechanism ( 11 ), to determine a target operating speed of the torque generating machine ( 4 ), to control the operating speed of the torque generating machine ( 4 ) in dependence on the determined target operating speed and to close the second decoupling mechanism ( 12 ) when the operating speed of the torque generating machine ( 4 ) at least substantially matches the determined target operating speed. The present invention also relates to a corresponding method of controlling first and second decoupling mechanisms ( 11, 12 ) to control the transmittal of torque from a torque generating machine ( 4 ) to one or more driven wheel of a vehicle ( 1 ).

TECHNICAL FIELD

The present disclosure relates to a vehicle apparatus and a method. Moreparticularly, but not exclusively, the vehicle apparatus is operableselectively to couple and decouple the vehicle driveline; and the methodrelates to the selective coupling and decoupling of the vehicledriveline.

BACKGROUND

It is known to disconnect a vehicle driveline and to reduce an operatingspeed of an internal combustion engine to reduce fuel consumption. Thisstrategy is known variously as vehicle gliding, vehicle sailing, idlecoasting etc. The operating mode is referred to herein as a glidingmode.

An example of a known driveline disconnect strategy is disclosed in theApplicant's earlier UK patent application GB1316183.1. A rear-wheeldrive vehicle 1 having a powertrain 3 is illustrated in FIG. 1. Thepowertrain 3 comprises an internal combustion engine 4, a transmission 5and a driveline 6. When a gliding mode is activated, the driveline 6 isdecoupled from the internal combustion engine 4. The operating speed ofthe internal combustion engine 4 can then be reduced, for example tooperate at idle, to provide improved fuel efficiency. When the internalcombustion engine 4 is decoupled, the driveline 6 is rotated by a torqueapplied by the driven wheels W_(D) (the rear wheels in the presentarrangement). The dynamic operating states of the respective componentswhen the vehicle 1 is operating in a conventional gliding mode areillustrated in FIG. 1.

A vehicle 1 having a front-wheel drive arrangement is illustrated inFIG. 2. The front-wheel drive vehicle 1 can also operate in a glidingmode by decoupling the driveline 6 from the internal combustion engine4. When the driveline 6 is decoupled, the driveline 6 is rotated by atorque applied by the driven wheels W_(D) (the front wheels in thepresent arrangement). The dynamic operating states of the respectivecomponents when the vehicle 1 is operating in a conventional glidingmode are illustrated in FIG. 2.

The relationship between the operating loads on a vehicle 1 travellingdown a 2% negative gradient is illustrated in FIG. 3. The loads areexpressed as the torque within a powertrain of the vehicle 1. Thepositive (accelerating) forces acting on the vehicle 1, represented by afirst arrow pointing in the direction of travel (from left to right inFIG. 2), comprise: an engine torque A delivered in dependence on adriver torque request; and an effective torque B derived from the roadgradient. The sum of the engine torque A and the effective torque Brepresents a total torque at the wheels of A+B. The negative(decelerating) forces acting on the vehicle 1, represented by a secondarrow pointing in the opposite direction (from right to left in FIG. 2),comprise: an aerodynamic torque C; a road loss torque D; an engine losstorque E; a transmission loss torque F; and a driveline loss torque G.The total negative torque is −(C+D+E+F+G); and the total positive torqueis (A+B). A first difference between the positive torque and thenegative torque is calculated as follows: (A+B)−(C+D+E+F+G). When thegliding mode is activated, the vehicle driveline 6 is disconnected fromthe internal combustion engine 4 and the total torque comprises apositive torque comprising the effective torque B; and a negative torquecomprising the aerodynamic torque C, the road loss torque D, thetransmission loss torque F and the driveline loss G. The internalcombustion engine 4 is disconnected from the driveline 6 so the engineloss torque E is not applied. A second difference between the positivetorque and the negative torque is calculated as follows: (B)−(C+D+F+G).The internal combustion engine can operate at a lower speed, for exampleidle, or can be switched off.

It would be advantageous to broaden the range of operating conditions inwhich the driveline could be decoupled from the internal combustionengine. It is against this backdrop that the present invention has beenconceived.

SUMMARY OF THE INVENTION

Aspects of the present invention relate to a vehicle operableselectively to couple and decouple a driveline; and to a method ofselectively coupling and decoupling a driveline of a vehicle as claimedin the appended claims.

According to a further aspect of the present invention there is provideda vehicle comprising:

-   -   a torque generating machine;    -   one or more driven wheel;    -   a driveline for transmitting torque from the torque generating        machine to said one or more driven wheel, the driveline        comprising a torque transmitting means;    -   a first decoupling mechanism operable to decouple the torque        transmitting means from the internal combustion engine, wherein        the first decoupling mechanism is closed to couple the torque        transmitting means to the internal combustion engine and is        opened to decouple the torque transmitting means from the        internal combustion engine;    -   a second decoupling mechanism operable to decouple the torque        transmitting means from the one or more driven wheel, wherein        the second decoupling mechanism is closed to couple the torque        transmitting means to the one or more driven wheel and is opened        to decouple the torque transmitting means from the one or more        driven wheel; and    -   a controller comprising at least one electronic processor for        controlling operation of the first and second decoupling        mechanisms. The arrangement of the first and second decoupling        mechanisms allows the torque transmitting means to be decoupled,        thereby providing a reduction in driveline losses. This        arrangement has particular application when the vehicle is        operating in a driveline disconnect gliding mode in which at        least a portion of the driveline can be decoupled and an        operating speed of the internal combustion engine may be        reduced.

The first decoupling mechanism comprises a first torque input means anda first torque output means. The first torque input means is connectedto the internal combustion engine. The first torque output means isconnected to the torque transmitting means. The first decouplingmechanism is operable selectively to transmit torque from said firsttorque input means to said first torque output means. The first torqueinput means may comprise a first input shaft; and the first torqueoutput means may comprise a first output shaft.

At least in certain embodiments, the first decoupling mechanism mayaccommodate slip to accommodate a speed differential between the firstinput means and the first output means. The first decoupling mechanismmay comprise one or more friction plate. The first decoupling mechanismmay comprise a first multi-plate clutch. In alternate arrangements, thefirst decoupling mechanism may be configured so as not to accommodateslip. The first decoupling mechanism can, for example, comprise one ormore of the following set: a torque converter, a single-plate clutch, amulti-plate clutch, a synchronizer, a hydrostatic coupling and amagnetic coupling.

The second decoupling mechanism comprises a second torque input meansand a second torque output means. The second torque input means isconnected to the one or more driven wheel. The second torque outputmeans is connected to the torque transmitting means. The seconddecoupling mechanism is operable selectively to transmit torque fromsaid second torque input means to said second torque output means. Thesecond torque input means may comprise a second input shaft; and thesecond torque output means may comprise a second output shaft.

At least in certain embodiments, the second decoupling mechanism mayaccommodate slip to accommodate a speed differential between the secondinput means and the second output means. The second decoupling mechanismmay comprise one or more friction plate.

The second decoupling mechanism may comprise one or more of thefollowing set: a torque converter, a single-plate clutch, a multi-plateclutch, a synchronizer, a hydrostatic coupling and a magnetic coupling.In alternate arrangements, the second decoupling mechanism may be anon-slip mechanism (i.e. a mechanism which does not accommodate slipbetween the second torque input means and the second torque outputmeans). The second decoupling mechanism can, for example, comprise a dogclutch disposed in series with an output of a differential; or a dogclutch disposed between a ring gear and a differential carrier.

The first and second decoupling mechanisms may be controlled to recouplethe torque transmitting means to the internal combustion engine and theone or more driven wheel.

The torque transmitting means is suitable for transmitting torque topropel the vehicle. The torque transmitting means may comprise a driveshaft. Alternatively, or in addition, the torque transmitting means maycomprise a differential, a torque transfer transmission, a transfer caseor a drive mechanism.

The at least one electronic processor may be configured to close thesecond decoupling mechanism to couple the torque transmitting means tothe one or more driven wheel. The at least one electronic processor maybe configured to start the torque generating machine. The at least oneelectronic processor may be configured to determine a target operatingspeed of the torque generating machine. The target operating speed maybe determined before, during or after the second decoupling mechanism isclosed. The at least one electronic processor may control an operatingspeed of the torque generating machine in dependence on the determinedtarget operating speed. The at least one electronic processor may closethe first decoupling mechanism when the operating speed of the torquegenerating machine at least substantially matches the determined targetoperating speed.

The target operating speed may be determined at least substantially tosynchronize the rotational speeds of the first input shaft and the firstoutput shaft. The rotational speed of the first output shaft isproportional to the rotational speed of the torque transmitting means.The rotational speed of the torque transmitting means may be measureddirectly, for example by a speed sensor. When the second decouplingmechanism is closed, the rotational speed of the torque transmittingmeans is proportional to the wheel speed. Thus, after the seconddecoupling mechanism is closed, the rotational speed of the torquetransmitting means may be determined based on the wheel speed of the oneor more driven wheel. The target operating speed may be determined independence on a wheel speed signal comprising a measured wheel speed ofthe one or more driven wheel. The first input shaft and the first outputshaft may be synchronized by matching the operating speed of the torquegenerating machine to the determined target operating speed.

The at least one electronic processor may be configured to receive atorque demand signal, for example generated in dependence on a throttlepedal position signal. The target operating speed may be determined independence on the torque demand signal. The internal combustion enginemay deliver a requested torque when the first decoupling mechanism isclosed. In this arrangement, the first decoupling mechanism shouldprovide slip to accommodate any speed differential between the firstinput shaft and the first output shaft when the first decouplingmechanism is closed.

The at least one electronic processor may be configured to start thetorque generating machine when the first torque decoupling mechanism isopen. The at least one electronic processor may be configured todetermine a target operating speed of the torque generating machine. Thetarget operating speed may be determined at least substantially tosynchronize the rotational speeds of the first and second input shafts.The target operating speed may be determined in dependence on a wheelspeed signal comprising a measured wheel speed of the one or more drivenwheel. The target operating speed may be determined such that the firstand second input shafts rotate at substantially the same speed. The atleast one electronic processor may control the operating speed of thetorque generating machine in dependence on the determined targetoperating speed. The at last one electronic processor may be configuredto close the first decoupling mechanism when the operating speed of thetorque generating machine at least substantially matches the determinedtarget operating speed. The second decoupling mechanism may be closedafter closing the first decoupling mechanism. Once the first decouplingmechanism is closed, the second input shaft and the second output shaftrotate at substantially the same speed. In this arrangement, the seconddecoupling mechanism does not have to accommodate slip since the secondinput shaft and the second output shaft are rotating at substantiallythe same speed when the second decoupling mechanism is closed.

The at least one electronic processor may be configured to start thetorque generating machine when the first torque decoupling mechanism isopen. The at least one electronic processor may be configured to closethe first decoupling mechanism. The at least one electronic processormay determine a target operating speed of the torque generating machine.After closing the first decoupling mechanism, the at least oneelectronic processor may control the operating speed of the torquegenerating machine in dependence on the determined target operatingspeed. The target operating speed may be determined in dependence on awheel speed signal comprising a measured wheel speed of the one or moredriven wheel. The target operating speed may be determined such that thefirst and second input shafts rotate at substantially the same speed.The at least one electronic processor may be configured to close thesecond decoupling mechanism when the operating speed of the torquegenerating machine at least substantially matches the determined targetoperating speed. In this arrangement, the second decoupling mechanismdoes not have to accommodate slip since the second input shaft and thesecond output shaft are rotating at substantially the same speed whenthe second decoupling mechanism is closed.

The at least one electronic processor may be configured to determine thetarget operating speed of the torque generating machine in dependence onthe wheel speed signal such that a rotational speed of the torquetransmitting means is synchronised with a wheel speed represented by thewheel speed signal.

The vehicle may comprise a transmission coupled to the torque generatingmachine. The transmission comprises is operable to select one of aplurality of gear ratios. The transmission may be an automatictransmission. The first decoupling mechanism may be incorporated intothe transmission. Alternatively, the first decoupling mechanism may bedisposed between the internal combustion engine and the transmission; orbetween the transmission and the torque transmitting means.

The torque generating machine may comprise an internal combustionengine.

The controller may be configured to activate a driveline disconnectgliding mode by opening the first decoupling mechanism to decouple thetorque transmitting means from the torque generating machine and openingthe second decoupling mechanism to decouple the torque transmittingmeans from the one or more driven wheel.

According to a further aspect of the present invention there is provideda method of controlling first and second decoupling mechanisms tocontrol the transmittal of torque from a torque generating machine toone or more driven wheel of a vehicle; the method comprising:

-   -   opening the first decoupling mechanism to decouple the torque        transmitting means from the internal combustion engine;    -   opening the second decoupling mechanism to decouple the torque        transmitting means from the one or more driven wheel. The first        and second decoupling mechanisms may be opened simultaneously.        Alternatively, the first and second decoupling mechanisms may be        opened sequentially. The first decoupling mechanism may be        opened before the second decoupling mechanism; or the second        decoupling mechanism may be opened before the first decoupling        mechanism.

The method may comprise:

-   -   closing the second decoupling mechanism to couple the torque        transmitting means to the one or more driven wheel;    -   determining a target operating speed of the torque generating        machine;    -   controlling an operating speed of the torque generating machine        in dependence on the determined target operating speed; and    -   closing the first decoupling mechanism when the operating speed        of the torque generating machine at least substantially matches        the determined target operating speed.

The target operating speed of the torque generating machine may bedetermined after closing the second decoupling mechanism. The targetoperating speed of the torque generating machine may be determined independence on a wheel speed signal.

Alternatively, or in addition, the method may comprise determining thetarget operating speed of the torque generating machine in dependence ona torque demand request made by a driver of the vehicle.

The method may comprise:

-   -   determining a target operating speed of the torque generating        machine;    -   controlling the operating speed of the torque generating machine        in dependence on the determined target operating speed;    -   closing the first decoupling mechanism when the operating speed        of the torque generating machine at least substantially matches        the determined target operating speed; and    -   closing the second decoupling mechanism after closing the first        decoupling mechanism.

The method may comprise:

-   -   closing the first decoupling mechanism;    -   determining a target operating speed of the torque generating        machine;    -   controlling the operating speed of the torque generating machine        in dependence on the determined target operating speed; and    -   closing the second decoupling mechanism when the operating speed        of the torque generating machine at least substantially matches        the determined target operating speed.

The target operating speed of the torque generating machine may bedetermined in dependence on a wheel speed signal.

The first decoupling mechanism may comprise a first torque input meansand a first torque output means. The first decoupling mechanism maycomprise a slipping mechanism for accommodating slip between said firsttorque input means and said first torque output means. For example, thefirst decoupling mechanism may comprise one or more friction plate foraccommodating slip.

The second decoupling mechanism may comprise a second torque input meansand a second torque output means. The second decoupling mechanism maycomprise a non-slip mechanism which does not accommodate slip betweensaid first torque input means and said first torque output means. Thesecond decoupling mechanism can, for example, comprise a torqueconverter, a single-plate clutch, a multi-plate clutch, a synchronizer,a hydrostatic coupling or a magnetic coupling.

Any controller or controllers described herein may suitably comprise acontrol unit or computational device having one or more electronicprocessors. Thus the system may comprise a single control unit orelectronic controller or alternatively different functions of thecontroller may be embodied in, or hosted in, different control units orcontrollers. As used herein the term “controller” or “control unit” willbe understood to include both a single control unit or controller and aplurality of control units or controllers collectively operating toprovide any stated control functionality. To configure a controller, asuitable set of instructions may be provided which, when executed, causesaid control unit or computational device to implement the controltechniques specified herein. The set of instructions may suitably beembedded in said one or more electronic processors. Alternatively, theset of instructions may be provided as software saved on one or morememory associated with said controller to be executed on saidcomputational device. A first controller may be implemented in softwarerun on one or more processors. One or more other controllers may beimplemented in software run on one or more processors, optionally thesame one or more processors as the first controller. Other suitablearrangements may also be used.

Within the scope of this application it is expressly intended that thevarious aspects, embodiments, examples and alternatives set out in thepreceding paragraphs, in the claims and/or in the following descriptionand drawings, and in particular the individual features thereof, may betaken independently or in any combination. That is, all embodimentsand/or features of any embodiment can be combined in any way and/orcombination, unless such features are incompatible. The applicantreserves the right to change any originally filed claim or file any newclaim accordingly, including the right to amend any originally filedclaim to depend from and/or incorporate any feature of any other claimalthough not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the present invention will now be described,by way of example only, with reference to the accompanying figures, inwhich:

FIG. 1 shows a schematic representation of the main components of aconventional rear-wheel drive vehicle;

FIG. 2 shows a schematic representation of the main components of aconventional front-wheel drive vehicle;

FIG. 3 shows a schematic representation of the forces acting on avehicle when operating in a gliding mode;

FIG. 4 shows a schematic representation of a vehicle configured tooperate in a driveline disconnect gliding mode in accordance with anembodiment of the present invention;

FIG. 5 shows a schematic representation of the dynamic operating statesof the components in the driveline of the vehicle shown in FIG. 4 whenoperating in said driveline disconnect gliding mode;

FIG. 6 shows a schematic representation of the loads on the vehicleshown in FIG. 4 when operating in the said driveline disconnect glidingmode;

FIG. 7 shows a schematic representation of a front-wheel drive vehicleoperating in a driveline disconnect gliding mode in accordance with anembodiment of the present invention;

FIG. 8 shows a schematic representation of the transmission and frontdifferential of the front-wheel drive vehicle shown in FIG. 7; and

FIG. 9 shows a schematic representation of a four-wheel drive vehicleoperable in a driveline disconnect gliding mode in accordance with anembodiment of the present invention.

DETAILED DESCRIPTION

A vehicle 1 comprising a controller 2 according to an embodiment of thepresent invention will now be described with reference to FIGS. 4, 5 and6. The controller 2 is configured selectively to activate and deactivatea driveline disconnect gliding mode. In the present embodiment, thevehicle 1 is a rear-wheel drive automobile having driven wheels W_(D)disposed at the rear. It will be appreciated that the inventiondescribed herein is not limited to this drive configuration. Moreover,the invention can be implemented in different types of vehicle.

As illustrated in FIG. 4, the vehicle 1 comprises a powertrain 3 forgenerating a traction force to propel the vehicle 1. The powertrain 3comprises an internal combustion engine 4, a transmission 5 and adriveline 6. The internal combustion engine 4 is arranged in alongitudinal configuration (North South) in the vehicle 1. Thetransmission 5 is an automated transmission comprising one or moreinternal friction brake; and one or more multi-plate clutch. Thetransmission 5 is controlled by a transmission control module (TCM) 7.The driveline 6 is arranged to transmit torque from the internalcombustion engine 4 to driven wheels W_(D). In the present embodiment,the driveline 6 is configured to transmit torque to the rear wheels ofthe vehicle 1. The powertrain 3 could optionally also include anelectric traction machine (not shown) for supplying a traction force tosaid driven wheels W_(D).

The driveline 6 comprises a torque transmitting means for transmittingtorque from the internal combustion engine 4 to the driven wheels W_(D).In the present embodiment, the torque transmitting means is in the formof a drive shaft 8. The drive shaft 8 is selectively coupled to thedriven wheels W_(D) by first and second rear half shafts 9, 10. Thevehicle 1 comprises a first decoupling mechanism 11 and a seconddecoupling mechanism 12. The first and second decoupling mechanisms 11,12 are disposed at opposite ends of the drive shaft 8 and, as describedherein, can be controlled independently of each other. As describedherein, the controller 2 is configured to control operation of the firstand second decoupling mechanisms 11, 12.

The first decoupling mechanism 11 comprises a first input means in theform of a first input shaft; and a first output means in the form of afirst output shaft. The internal combustion engine 4 transmits an inputtorque to the first input shaft; and the first output shaft transmits anoutput torque to the drive shaft 8. The first decoupling mechanism 11 isoperable selectively to couple and decouple the drive shaft 8 from theinternal combustion engine 4. The first decoupling mechanism 11 isopened to decouple the first input shaft from the first output shaft,thereby decoupling the drive shaft 8 from the internal combustion engine4. Conversely, the first decoupling mechanism 11 is closed to couple thefirst input shaft to the first output shaft, thereby coupling the driveshaft 8 to the internal combustion engine 4. The first decouplingmechanism 11 is implemented by controlling operation of the transmission5, for example by opening a clutch in the transmission 5 to disconnectthe drive shaft 8 from the internal combustion engine 4. In a variant,the first decoupling mechanism 11 can be separate from the transmission5. For example, the first decoupling mechanism 11 can be disposedbetween the drive shaft 8 and the transmission 5; or between theinternal combustion engine 4 and the transmission 5.

The second decoupling mechanism 12 comprises a second input means in theform of a second input shaft; and a second output means in the form of asecond output shaft. The drive shaft 8 transmits torque to the secondinput shaft; and the second output shaft transmits a torque to first andsecond rear half shafts 9, 10 to drive the driven wheels W_(D). Thesecond output shaft can, for example, transmit torque to a reardifferential 13 configured to transmit torque to the first and secondrear half shafts 9, 10. When the internal combustion engine 4 isdecoupled from the drive shaft 8 (i.e. the first decoupling mechanism 11is open), the first and second rear half shafts 9, 10 transmit torque tothe second output shaft of the second decoupling mechanism 12. Thesecond decoupling mechanism 12 is operable to decouple the drive shaft 8from the driven wheels W_(D). The second decoupling mechanism 12 isclosed to couple the second input shaft to the second output shaft,thereby coupling the drive shaft 8 to the driven wheels W_(D).Conversely, the second decoupling mechanism 12 is opened to decouple thesecond input shaft from the second output shaft, thereby decoupling thedrive shaft 8 from the driven wheels W_(D). In the present embodimentthe second decoupling mechanism 12 comprises a multi-plate clutch. Themulti-plate clutch allows slip between the second input shaft and thesecond output shaft to compensate for the different rotational speeds ofthe drive shaft 8 and the first and second rear half shafts 9, 10 whenthe driveline disconnect gliding mode is deactivated. In a modifiedarrangement, the second decoupling mechanism 12 can comprise first andsecond clutch mechanisms associated with the first and second rear halfshafts 9, 10 respectively. The first and second clutch mechanisms can,for example, be incorporated into the rear differential 13.

The controller 2 comprises at least one electronic processor Pconfigured to execute a set of computational instructions stored on anon-transitory computer readable media. The controller 2 monitors one ormore vehicle dynamic conditions, such as vehicle acceleration and/orspeed; and one or more vehicle operating parameters, such as outputtorque from the internal combustion engine 4. The controller 2 isconfigured to identify a vehicle glide opportunity when the measureddynamic condition(s) differs from a desired vehicle dynamic conditionfor the current vehicle operating parameter(s). The controller 2 canalso check to identify a positive torque request indicative of a driverintention to maintain the current vehicle dynamic conditions. When theseconditions are satisfied, the controller 2 publishes an activationsignal S_(ACT) to a vehicle communications network COM to activate adriveline disconnect gliding mode. In dependence on the activationsignal S_(ACT), the first decoupling mechanism 11 is opened to decouplethe drive shaft 8 from the internal combustion engine 4; and the seconddecoupling mechanism 12 is opened to decouple the drive shaft 8 from thefirst and second rear half shafts 9, 10. A powertrain control module(PCM) also operates to reduce the torque request of the internalcombustion engine 4. The internal combustion engine 4 can operate atidle during the driveline disconnect gliding mode or can be shut down byinhibiting the combustion cycle. By opening both the first and seconddecoupling mechanisms 11, 12, the rotational speed of the drive shaft 8decreases and, depending on the duration of the driveline disconnectgliding mode, can come to rest. As the driveline 6 is not coupled to thedriven wheels W_(D) when the second decoupling mechanism 12 is open, thetotal losses acting on the vehicle 1 can be reduced. At least in certainembodiments, this enables activation of the driveline disconnect glidingmode over a broader range of operating conditions.

With reference to FIG. 4, the at least one processor P is configured toreceive a wheel speed signal S_(WH), an internal combustion engine speedsignal S_(ICE) and a torque request signal S_(TQ). The wheel speedsignal S_(WH) is generated by at least one wheel speed sensor 14associated with the driven wheels W_(D) of the vehicle 1. The internalcombustion engine speed signal S_(ICE) is generated by a crankshaftspeed sensor 15. The torque request signal S_(TQ) is generated independence on a pedal position sensor 16 associated with a throttlepedal 17. The torque request signal S_(TQ) comprises a torque demandsignal generated by a driver of the vehicle 1 when the throttle pedal 17is depressed. Alternatively, or in addition, the torque demand signalcan be generated by a cruise control system, for example to match atarget vehicle speed.

The transmission control module (TCM) 7 detects the activation signalS_(ACT) published to the communications network COM. In dependence onsaid activation signal S_(ACT), the transmission control module 7controls operation of the internal clutches in the transmission 5 todecouple the drive shaft 8 from the transmission 5. The seconddecoupling mechanism 12 is also opened to disconnect the drive shaft 8from the first and second rear half shafts 9, 10. The drive shaft 8 isthereby disconnected from the internal combustion engine 4 and from thedriven wheels W_(D). The first and second decoupling mechanisms 11, 12can be opened concurrently or sequentially to activate the drivelinedisconnect gliding mode. The internal combustion engine 4 is shut downby inhibiting the combustion cycle. As shown in FIG. 5, when the firstand second decoupling mechanisms 11, 12 are open, the drive shaft 8comes to rest. The operating speed of the internal combustion engine 4can be reduced, for example to an idle speed. It will be appreciatedthat the first and second rear half shafts 9, 10 continue to rotatesince the rotation of the driven wheels W_(D) transmits an input torque.

The operating loads acting on the vehicle 1 when the drivelinedisconnect gliding mode has been activated are shown schematically inFIG. 6. The first arrow 19 (pointing from left to right) represents thepositive forces acting on the vehicle 1. The same deceleration rate isachievable by activating the driveline disconnect gliding mode inaccordance with an aspect of the present invention. The effective torqueB is delivered by virtue of the negative gradient on which the vehicle 1is travelling. The positive contribution of the engine torque A isremoved since the transmission 5 selects neutral and the internalcombustion engine 4 is slowed to idle speed or is stopped. The secondarrow 20 (pointing from right to left) represents the negative (i.e.decelerating) forces. The negative contributions of the engine losstorque E and the transmission loss torque F are removed. The drivelineloss torque G is at least partially removed since the drive shaft 8 isdecoupled from the internal combustion engine 4 and the driven wheel W.The total positive torque is provided by the effective torque B, and thetotal negative torque comprises the aerodynamic torque C and the roadloss torque D, i.e. −(C+D). A second difference between the positivetorque and the negative torque is calculated as follows: (B)−(C+D). Byremoving the driveline loss torque G, the range of operating conditionsin which the driveline disconnect gliding mode can usefully be activatedis increased, for example to allow activation at smaller gradients.

The controller 2 monitors the vehicle dynamic conditions and the vehicleoperating parameters to determine when the driveline disconnect glidingmode is no longer appropriate (i.e. when the effective torque B is nolonger sufficient to compensate for the aerodynamic torque C and theroad loss torque D. The controller 2 then deactivates the drivelinedisconnect gliding mode. The controller 2 implements a first controlstrategy to couple the drive shaft 8 to the driven wheels W_(D) and tothe internal combustion engine 4. Specifically, the controller 2 closesthe second decoupling mechanism 12 to couple the drive shaft 8 to thedriven wheels W_(D) by the first and second rear half shafts 9, 10. Thedrive shaft 8 is decoupled during the driveline disconnect gliding modeand has a lower rotational speed than the driven wheels W_(D). Indeed,the rotational speed of the drive shaft 8 may be zero (0) during thedriveline disconnect gliding mode. The multi-plate clutch arrangement ofthe second decoupling mechanism 12 allows slip between the second inputshaft and the second output shaft. The second decoupling mechanism 12closes and the rotational speed of the drive shaft 8 increases inproportion to the rotational speed of the first and second rear halfshafts 9, 10 which are drivingly connected to the driven wheels W_(D).The controller 2 initiates an engine start-up procedure, for example byactivating a starter motor (not shown), to re-start the internalcombustion engine 4. The engine start-up procedure can be performedconcurrently with closing of the second decoupling mechanism 12. Afterthe second decoupling mechanism 12 is closed, the controller 2determines the rotational speed of the drive shaft 8. The rotationalspeed of the drive shaft 8 could be measured directly, for example usinga dedicated speed sensor. However, in the present embodiment therotational speed of the drive shaft 8 is determined in dependence on themeasured wheel speed (as indicated by the wheel speed signal SWH) whichis proportional to the rotational speed of the drive shaft 8. Thecontroller 2 then determines a target operating speed for the internalcombustion engine 4 at least substantially to match the rotational speedacross the first decoupling mechanism 11. The controller 2 outputs anengine speed request signal in dependence on the determined targetoperating speed. Once the operating speed of the internal combustionengine 4 at least substantially matches the target operating speed, thecontroller 2 outputs a control signal to close the first decouplingmechanism 11. The driveline 6 is thereby re-coupled to the internalcombustion engine 4 and to the driven wheels W_(D).

The control strategy described above to terminate the drivelinedisconnect gliding mode requires that the second decoupling mechanism 12allows slip between the second input shaft and the second output shaftto accommodate the different rotational speeds of the drive shaft 8 andthe first and second rear half shafts 9, 10 when the drivelinedisconnect gliding mode is deactivated. In the present embodiment, thesecond decoupling mechanism 12 comprises a multi-plate clutch to allowslip. A first variant which does not require the second decouplingmechanism 12 to provide slip will now be described. In the firstvariant, the second decoupling mechanism 12 can, for example, comprise adog clutch disposed in series with an output of a differential; or a dogclutch disposed between a ring gear and a differential carrier. Thecontroller 2 is configured to activate the driveline disconnect glidingmode by opening the first and second decoupling mechanisms 11, 12 todecouple the drive shaft 8. The first and second decoupling mechanisms11, 12 may be opened simultaneously to decouple the drive shaft 8 orsequentially. Alternative control strategies implemented for the firstvariant to deactivate the driveline disconnect gliding mode will now bedescribed. In a further variant, if the internal combustion engine 3 isstopped and comes to rest during the driveline disconnect gliding mode,the first decoupling mechanism 11 can be closed concurrent with orbefore the internal combustion engine 3 is re-started. This controlstrategy would allow the drive shaft 8 to be coupled to the internalcombustion engine 3 when the rotational speeds are similar, potentiallyboth zero.

A second control strategy for deactivating the driveline disconnectgliding mode will now be described. The controller 2 determines a targetoperating speed for the internal combustion engine 4 in dependence onthe measured wheel speed of the driven wheels W_(D). In particular, thetarget operating speed is determined such that the input rotationalspeed of the first decoupling mechanism 11 is substantially the same asthe input rotational speed of the second decoupling mechanism 12 (whichis proportional to the wheel speed of the driven wheels W_(D)). When theoperating speed of the internal combustion engine 4 matches the targetoperating speed, the first decoupling mechanism 11 is closed. The firstdecoupling mechanism 11 accommodates slip, thereby allowing therotational speed of the drive shaft 8 to increase progressively to matchthe input rotational speed of the first decoupling mechanism 11. Bycontrolling the operating speed of the internal combustion engine 4, therotational speed of the drive shaft 8 can be at least substantiallymatched to the output rotational speed of the second decouplingmechanism 12. Once the rotational speed have been matched, the seconddecoupling mechanism 12 is closed to re-couple the drive shaft 8 to thedriven wheels W_(D) via the first and second rear half shafts 9, 10. Bycontrolling the operating speed of the internal combustion engine 4 tosynchronise the rotational speed of the drive shaft 8 to the outputrotational speed of the second decoupling mechanism 12, a non-slipcoupling mechanism can be utilised.

A third control strategy for deactivating the driveline disconnectgliding mode will now be described. The internal combustion engine 4 isre-started. The first decoupling mechanism 11 is closed to couple thedrive shaft 8 to the internal combustion engine 4. The first decouplingmechanism 11 accommodates slip, thereby allowing the rotational speed ofthe drive shaft 8 to increase progressively to match the inputrotational speed of the first decoupling mechanism 11. The controller 2then determines a target operating speed for the internal combustionengine 4 in dependence on the measured wheel speed of the driven wheelsW_(D). The target operating speed is determined such that the inputrotational speed of the first decoupling mechanism 11 is substantiallythe same as the input rotational speed of the second decouplingmechanism 12 (which is proportional to the wheel speed of the drivenwheels W_(D)). When the operating speed of the internal combustionengine 4 matches the target operating speed, the second decouplingmechanism 12 is closed to re-couple the drive shaft 8 to the drivenwheels W_(D) via the first and second rear half shafts 9, 10. Bycontrolling the operating speed of the internal combustion engine 4, therotational speed of the drive shaft 8 can be at least substantiallymatched to the input rotational speed of the second decoupling mechanism12. It will be understood that controlling the operating speed of theinternal combustion engine 4 to synchronise the rotational speed of thedrive shaft 8 to the input rotational speed of the second decouplingmechanism 12 allows use of a non-slip coupling mechanism.

The second and third control strategies are both applicable to thevariant of the second decoupling mechanism 12 described above which doesnot permit slip between the second input shaft and the second outputshaft. It will be appreciated, however, that the second control strategycould also be applied to arrangements in which the second decouplingmechanism 12 does permit slip.

The vehicle 1 in the above embodiment has a rear-wheel drivearrangement. The invention described herein is equally applicable to avehicle 1 having a front-wheel drive arrangement. A further embodimentof the present invention implemented in a vehicle 1 having a front-wheeldrive arrangement will now be described with reference to FIGS. 7 and 8.Like reference numerals will be used for like components in thedescription of this arrangement.

As shown in FIG. 7, the vehicle 1 comprises a powertrain 3 forgenerating a traction force to propel the vehicle 1. The powertrain 3comprises an internal combustion engine 4, a transmission 5 and adriveline 6. The internal combustion engine 4 is arranged in atransverse configuration (East West) in the vehicle 1. The transmission5 is an automated transmission comprising one or more internal frictionbrake; and one or more multi-plate clutch. The driveline 6 is arrangedto transmit torque from the internal combustion engine 4 to drivenwheels W_(D). In the present embodiment, the driveline 6 is configuredto transmit torque to the front wheels of the vehicle 1.

The driveline 6 comprises a torque transmitting means for transmittingtorque from the internal combustion engine 4 to the driven wheels W_(D).With reference to FIG. 8, the torque transmitting means comprises afront differential 21 drivingly connected to the transmission 5. Inparticular, the front differential 21 comprises an input ring gear 22which meshes with an output gear 23 of the transmission 5. The frontdifferential 21 comprises first and second output shafts 24, 25 coupledto respective first and second front half shafts 26, 27. In use, thefirst and second front half shafts 26, 27 transmit torque to the drivenwheels W_(D) of the vehicle 1.

In accordance with the other embodiments described herein, the vehicle 1comprises a first decoupling mechanism 11 and a second decouplingmechanism 12. The first and second decoupling mechanisms 11, 12, can beselectively opened to decouple the front differential 21 from thedriveline 6 when the vehicle 1 is operating in a driveline disconnectgliding mode. The first and second decoupling mechanisms 11, 12 can becontrolled independently of each other. For example, the first andsecond decoupling mechanisms 11, 12 can be opened simultaneously orsequentially. As described herein, the controller 2 is configured tocontrol operation of the first and second decoupling mechanisms 11, 12.

The transmission 5 transmits an input torque to the input ring gear 22;and the differential transmits an output torque to the front half shafts26, 27. The first decoupling mechanism 11 is operable selectively tocouple and decouple the front differential 21 to the transmission 5.

The first decoupling mechanism 11 is incorporated into the transmission5. The first decoupling mechanism 11 may be associated with atransmission input shaft 28 which is connected to the internalcombustion engine 4. This arrangement of the first decoupling mechanismis denoted by the reference 11 a in FIG. 8. Alternatively, the firstdecoupling mechanism 11 may be incorporated into the transmission 5, forexample by selecting neutral or opening a transmission clutch, asdenoted by the reference 11 b in FIG. 8. In a further alternative, thefirst decoupling mechanism 11 may be incorporated into the transmission5 before a gear driving an intermediate shaft 29 within the transmission5, as denoted by the reference 11 c in FIG. 8. Alternatively, the firstdecoupling mechanism 11 may be incorporated into the intermediate shaftof the transmission 5, as denoted by the reference 11 d in FIG. 8. Thesevariations on the first decoupling mechanism 11 may be incorporated intothe other embodiments described herein.

The front differential 21 transmits torque to the first and second fronthalf shafts 26, 27 to drive the driven wheels W_(D). The seconddecoupling mechanism 12 is operable selectively to couple and decouplethe first and second output shafts 24, 25 to the respective first andsecond front half shafts 26, 27. The second decoupling mechanism 12 inthe present embodiment comprises first and second output decouplingmechanisms 12 a, 12 b which can be opened to decouple the first andsecond output shafts 24, 25 from the first and second front half shafts26, 27. The second decoupling mechanism 12 is operable to decouple thetransmission 5 and the front differential 21 from the driven wheelsW_(D). The second decoupling mechanism 12 in this embodiment is operableto disconnect both sides of the front differential 21. The first andsecond output decoupling mechanisms 12 a, 12 b may be operated togetheror independently of each other. The first and second output decouplingmechanisms 12 a, 12 b in the present embodiment are incorporated intothe front differential 21. However, it will be appreciated that thefirst and second output decoupling mechanisms 12 a, 12 b may be separatefrom the front differential 21, for example disposed between the frontdifferential 21 and the first and second front half shafts 26, 27.

The controller 2 in this further embodiment is configured to implementthe first control strategy described herein. When the drivelinedisconnect gliding mode is activated, the first and second decouplingmechanisms 11, 12 are open such that the front differential 21 and thetransmission 5 are decoupled from the driveline 6. In further variants,the second decoupling mechanism 12 can comprise one or more non-slipmechanisms. The controller 2 can be configured to implement the secondand third control strategies described herein to deactivate thedriveline disconnect gliding mode.

In certain modified arrangements, the second decoupling mechanism 12 mayprovide a single-side disconnect. The second decoupling mechanism 12 maycomprise a single output decoupling mechanism (either the first outputdecoupling mechanism 12 a or the second output decoupling mechanism 12b) which may be opened to decouple the front differential 21. In thisarrangement, the front differential 21 may rotate when the outputdecoupling mechanism 12 is opened.

In a further modified arrangement, the second decoupling mechanism 12may be associated with the input ring gear 22 of the front differential21. This arrangement of second decoupling mechanism is denoted by thereference 12 c in FIG. 8. The second decoupling mechanism 12 c is openedto decouple the input ring gear 22. Conversely, the second decouplingmechanism 12 c is closed to couple the input ring gear 22.

At least some of the features described herein with reference to thefront differential 21 may be incorporated into the rear differential 13described with reference to the rear-wheel drive embodiments of thepresent invention. For example, the second decoupling mechanism 12described with reference to the front differential 21 may beincorporated into the rear differential 13 to enable the first andsecond rear half shafts 9, 10 to be selectively coupled and decoupled.

The vehicle 1 may comprise one or more electric traction motor. Thevehicle 1 may, for example, be a Mild Hybrid Electric Vehicle (MHEV) ora Plug-in Hybrid Electric Vehicle (PHEV). The one or more electrictraction motor may, for example, be incorporated into the transmission 5or the driveline 6. The one or more electric traction motor could, forexample, be coupled to the transmission input shaft 28, the transmissionintermediate shaft or the transmission output shaft.

Aspects of the invention described herein could also be implemented in afour-wheel drive vehicle having front and rear driven wheels W_(D). Avehicle 1 having four-wheel drive and comprising first and seconddecoupling mechanisms 11, 12 in accordance with an embodiment of thepresent invention is shown in FIG. 9. The vehicle 1 comprises a transfercase 30 drivingly connected to the transmission 5. A front driveshaft 31connects the transfer case 30 to the first and second front half shafts26, 27. The first decoupling mechanism 11 is incorporated into thetransfer case 30 and is operable to disconnect the front driveshaft 31from the transfer case 30. The second decoupling mechanism 12 comprisesfirst and second output decoupling mechanisms 12 a, 12 b associated withthe first and second front half shafts 26, 27 respectively. When thevehicle 1 is operating in a driveline disconnect gliding mode, the firstdecoupling mechanism 11 is opened to disconnect the transfer case 30from the front driveshaft 31; and the first and second output decouplingmechanisms 12 a, 12 b are opened to disconnect the first and secondfront half shafts 26, 27 from the front driveshaft 31. The frontdriveshaft 31 may thereby be disconnected from the internal combustionengine 3 and the front driven wheels W_(D) when the driveline disconnectgliding mode is activated. It will be appreciated that additionaldecoupling mechanisms may be provided for disconnecting the driveshaft 8from the rear driven wheels W_(D). For example, the mechanisms describedherein with reference to the rear-wheel drive vehicle 1 shown in FIG. 5may be implemented in the four-wheel drive vehicle 1 shown in FIG. 9.The four-wheel drive function of the vehicle 1 may be permanentlyengaged. Alternatively, the four-wheel vehicle function of the vehicle 1may be selectively four-wheel drive, for example operating in two-wheeldrive under normal operating conditions. The activation of the drivelinedisconnect gliding mode may be controlled in dependence on whether thevehicle 1 is operating in four-wheel drive or two-wheel drive.

It will be appreciated that various changes and modifications can bemade to embodiments described herein without departing from the scope ofthe present invention.

The invention claimed is:
 1. A vehicle comprising: a torque generatingmachine; at least one driven wheel; a driveline for transmitting torquefrom the torque generating machine to said at least one driven wheel,the driveline comprising a torque transmitting means; a first decouplingmechanism operable to decouple the torque transmitting means from thetorque generating machine, wherein the first decoupling mechanism isclosed to couple the torque transmitting means to the torque generatingmachine and is opened to decouple the torque transmitting means from thetorque generating machine; a second decoupling mechanism operable todecouple the torque transmitting means from the at least one drivenwheel, wherein the second decoupling mechanism is closed to couple thetorque transmitting means to the at least one driven wheel and is openedto decouple the torque transmitting means from the at least one drivenwheel; and a controller comprising at least one electronic processor forcontrolling operation of the first and second decoupling mechanisms,wherein the at least one electronic processor is configured to: closethe first decoupling mechanism; determine a target operating speed ofthe torque generating machine; after closing the first decouplingmechanism, control the operating speed of the torque generating machinein dependence on the determined target operating speed; and close thesecond decoupling mechanism when the operating speed of the torquegenerating machine at least substantially matches the determined targetoperating speed.
 2. The vehicle as claimed in claim 1, wherein the firstdecoupling mechanism comprises first torque input means and first torqueoutput means, wherein the first decoupling mechanism accommodates slipbetween the first torque input means and the first torque output means.3. The vehicle as claimed in claim 1, wherein the at least oneelectronic processor is configured to determine the target operatingspeed of the torque generating machine in dependence on a wheel speedsignal.
 4. A vehicle as claimed in claim 1, wherein the seconddecoupling mechanism comprises second torque input means and secondtorque output means, wherein the second decoupling mechanism is anon-slip mechanism.
 5. The vehicle as claimed in claim 4, wherein thesecond decoupling mechanism comprises one or more of the following set:a torque converter, a single-plate clutch, a multi-plate clutch, asynchronizer, a hydrostatic coupling and a magnetic coupling.
 6. Thevehicle as claimed in claim 1, comprising a transmission coupled to thetorque generating machine, wherein the first decoupling mechanism isincorporated into the transmission.
 7. The vehicle as claimed in claim1, comprising a transmission coupled to the torque generating machine,wherein the first decoupling mechanism is disposed between the torquegenerating machine and the transmission or between the transmission andthe torque transmitting means.
 8. The vehicle as claimed in claim 1,wherein the first decoupling mechanism comprises one or more of thefollowing set: a torque converter, a single-plate clutch, a multi-plateclutch, a synchronizer, a hydrostatic coupling and a magnetic coupling.9. The vehicle as claimed in claim 1, wherein the torque generatingmachine comprises an internal combustion engine.
 10. The vehicle asclaimed in claim 1, wherein the controller is configured to activate adriveline disconnect gliding mode by opening the first decouplingmechanism to decouple the torque transmitting means from the torquegenerating machine and opening the second decoupling mechanism todecouple the torque transmitting means from the at least one drivenwheel.
 11. A method of controlling first and second decouplingmechanisms to control a transmittal of torque from a torque generatingmachine to at least one driven wheel of a vehicle; the methodcomprising: opening the first decoupling mechanism to decouple torquetransmitting means from the torque generating machine; opening thesecond decoupling mechanism to decouple the torque transmitting meansfrom the at least one driven wheel; closing the first decouplingmechanism; determining a target operating speed of the torque generatingmachine; after closing the first decoupling mechanism, controlling theoperating speed of the torque generating machine in dependence on thedetermined target operating speed; and closing the second decouplingmechanism when the operating speed of the torque generating machine atleast substantially matches the determined target operating speed. 12.The method as claimed in claim 11, comprising determining the targetoperating speed of the torque generating machine in dependence on awheel speed signal.
 13. The method as claimed in claim 11, wherein thesecond decoupling mechanism comprises second torque input means andsecond torque output means; the method comprising at least substantiallymatching a rotational speed of the second torque input means and thesecond torque output means and then closing the second decouplingmechanism.
 14. The method as claimed in claim 11, comprising activatinga driveline disconnect gliding mode by opening the first decouplingmechanism to decouple the torque transmitting means from the torquegenerating machine and opening the second decoupling mechanism todecouple the torque transmitting means from the at least one drivenwheel.
 15. A controller comprising at least one processor configured toimplement the method of claim 11.